On January 1, 1801 Father Giuseppe
Piazzi was observing for a new star catalogue a
collection of the precise location of all stars visible
in the sky. While observing stars in the constellation
Taurus, he saw a small, starlike object that was not
listed on any of his star maps. He carefully recorded its
location, but on the next night, he noticed that the
object had moved slightly to the east. Stars don't do
such a thing. Over the next six weeks he recorded its
motion, and discovered that it was moving relative to the
background stars. Its rapid motion indicated that the
object was not a star, but rather an object in the solar
system. The first asteroid was discovered.
Piazzi had discovered Ceres, the largest known asteroid
(roughly one-third the size of the moon). Three more
asteroids were discovered just years after--Pallas in
1802, Juno in 1804, and Vesta in 1807. Asteroid
discoveries were rare from then until 1891, when
photographic search methods were first introduced. click here for the full story

Ceres:
the missing planet? by Livia GiacominiIn the eighteen century, scientists
tried to find a mathematical formula to describe the
solar system and in particular, the distances from the
planets to the Sun. Johannes Titus
and Johann Elert Bode came up with a law (today called
Titus Bode's law) that at, that time, seemed to fit the
reality of the solar system.This empirical law predicted pretty
well the distances between the Sun and all the planets
known at that epoch (Neptune and Pluto, the farthest
ones, which don't respect it at all, have been discovered
only afterwards).

where :

is the distance (in A.U.)
of each planet from the Sun

N=0,1,2,4

doubles for every
successive planet of
the solar system

planet

N

predicted
distance

real
distance

Mercury

0

0.4

0.39

Venus

1

0.7

0.72

Earth

2

1.0

1.00

Mars

4

1.6

1.52

Gap

8

2.8

2.77

Jupiter

16

5.2

5.20

Saturn

32

10.0

9.54

Uranus

64

19.6

19.19

Neptune

128

38.8

30.07

Pluto

256

77.2

39.53

From
this law, however, there seemed to be a gap at 2.8 A.U.,
where a missing planet should have existed. At the end of
the year 1800, a search for this missing planet was to be
organized, when the first asteroid was found by Giuseppe
Piazzi and named after the patron goddess of Siciliy,
Ceres. Ceres was first believed to be the missing planet
that could confirm Titus Bode's law. But very soon other
bodies were discovered in the same region (Pallas in
1802, Juno in 1804 and Vesta in 1807). It soon became
clear that Titus-Bode's law had to be refused, and
between Mars and Jupiter, not just one, but many minor
planets had to exist (in what is today called the
asteroid's main belt). As soon as it was discovered, it
became necessary to compute the orbit of this new object,
so that it could be possible to observe it again in the
future. Here, again, Ceres was an innovation in the
asteroid's science: Piazzi wasn't able to observe it long
enough to compute it's orbit with the methods available.
It was only thanks to a great mathematician, Carl
Friedrich Gauss, who invented in that occasion a new
method for the calculation of orbits, that Ceres didn't
become lost. Using this new method, Wilhelm Olbers
predicted its position, and Ceres, which in the meanwhile
had become unobservable, was found again on december 31,
1801. The new method of calculus soon became a new
milestone of mathematical astronomy, being still used
today with some simple modifications.